The prior art discloses a number of adjustable devices for attaching noise suppressing ear mufflers to hard hats, varying the sealing pressure engagement thereof against the ears, disengaging and shifting the mufflers from the ears to a rest or stored position. However, the ear mufflers are adjustably or non adjustably mounted on adjustable flexible spring levers or support arms rotatably mounted on the hard hat for movement in vertical parallel planes. Hence, in the rest position the resilient lever support arms remain flexed or stressed and continue to press the ear mufflers against the side or crown of the hard hat.
Further, adjusting the spring lever or flexible support arm relative to its supporting bracket or the muffler relative to the arm varies the effective length and hence the pressure exerted by the arm against the mufflers and the engaging ear.
The applicants device is an improvement on a similar device disclosed in a pending application of another inventor and assigned to the same assignee. The improved device differs from the known prior art in that the support arm has limited vertical and angular adjustment in the wearing position and must be extended before it can be rotated to an assured non-flexed stored position. Further, each resilient support arm has a fixed point of pivotal connection with the muffler, begins to flex about the same point relative thereto and applies a substantially constant pressure regardless of the adjusted position relative to support bracket. Additionally, the support bracket attached to the hard hat is provided with means for directing the rotatable support arms and attached mufflers away from the crown of hard hat and thereby allowing the resilient lever arm to return to its initial unstressed and non flexed state.
Also, it is highly desirable that the hard hats and accessories attached thereto be made of non conductive dielectric materials such as plastics.
However, plastics including other material maintained under extended period of tension have a tendency to creep, lose some of their resiliency and the ability to fully recover and return to the initial state.
Therefor, it is desirable to relieve tension in the resilient muffler support arm when the ear mufflers are rotated to an inoperative or stored position, and thereby retain a substantially constant sufficient amount of resiliency and pressure exerted thereby to seal the mufflers about the ears.